Adjustable cam



March 23, 1948.

F. D. BURNS ADJUSTABLE CAM File d Dec; 22, 1943 MAX 0 00 C0/VD/770/V I INVENTOR.

cemm WW' Patented Mar. 23, 1948 ADJUSTABLE CAM Frank Donald Burns, Long Beach, Ind., assig'nor to The H a'ys Corporation, Michigan City, Ind,

a corporation of Indiana Application December 22, 1943, Serial No. 515,207

Claims. 1

This invention relates to an adjustable cam.

It is frequently desirable, in instruments and other devices of various types, to provide cams which may be adjusted within limited ranges to compensate for conditions or characteristics difiering somewhat from those for which the cam was designed and peculiar to the device or caused by factors inherent in the type or purpose of use, or in auxiliary or connected devices. An

example of such an instrument is a flow meter which uses a square root cam to cause the indicating or recording means of the instrument to operate properly relative to a scale having substantially equally spaced scale divisions. In some instances'the relation between flow and the condition which the instrument measures may not be a square root relation. Thus, if the air fiow in a boiler is being measured, the characteristics of the metering element or motor of the instrument, or some condition in the boiler such as the arrangement of battles therein, may cause a relationship which is below or above the square root relation. In such a case, the minimum and maximum values, for instance the zero and 100% values indicated by the instrument may remain accurate, but the intermediate values indicated by the instrument are inaccurate unless a cam designed to respond to the relationship which actually exists is used in the instrument.

Therefore, it is the primary object of this invention to provide a cam which is capable, by adjustment, of variation within predetermined limits of departure from the relation for which the cam element per se is shaped, while avoiding material change at either of the extremities of the camelement.

A further object is to provide adevice of this character which is inexpensive, simple in construction, and which can be adjusted quickly and with minimum requirements for manipulation of parts.

Other objects will be apparent from the description and appended claims.

In the drawing:

Fig. 1 is a view in front elevation of an instrument using my new cam, wherein the cover plate of the instrument isshown in open position.

Fig. 2 is an enlarged view of the cam in rear elevation.

Fig. 3 is an enlarged top edge view of the cam.

Fig. 4 is an enlarged side edge view of the cam.

Fig. 5 is a diagram illustrating theoperat'ion of the cam atvarious adjustments thereof.

I have elected to illustrate the invention as applied to a gas flow meter of the type illustrated in Fig. 1, wherein the meter is provided with a casing or enclosure 10 having a cover or face plate H pivoted thereto at H and mounting a frame l3 thereinfor supporting the various operative elements or components of the instrument. Frame l3 also mounts a scale l4 positioned in registration with a sight opening (not shown) in face plate l'l.

The instrument herein illustrated includes a suitable metering element 15, such as a device responsive to the difierence in pressure existing at two different points in some device, such as: a boiler, which pressures "are tapped to the metering element t5 at conduit portions I6 thereof. The metering element [5 actuates an elongated arm 11 pivoted thereto at l8. Arm l8 carries a contact l9 at its outer end. A second elongated arm 20 is suitably'pivotedto member I5 or to frame l3 at 2| aboutan axis parallel to the axis of pivot l8 and carries 'a contact 22 at its outer end which is adapted to engage the contact l9.

A reversible electric motor 23, such as a threelead capacitor type motor which hasa condenser (not shown) so connected across the leads thereof as to control the phase relation :of the field coils thereof, and therefore the direction of rotation thereof, according to whether one lead to the motor is open or closed, as is well understood in the'art, is mounted on frame I3. Switch 24 controls the operation of the motor. One lead to the motor includes conductors "25 carried by arms I! and 20 and connected to'the contacts 19 and 22, whereby said contacts form a switch which controls the direction of operation of motor 23. The arm 20 is connected with the motor by suitable means '(not shown) to be swung toward and from the-arm 11 according to the direction in which the motor operates, The parts are so arranged that when the contacts l9 and 22 are in engagement the motor 23 will be controlled to operate in adirection to swing arm 20 to the right Vie'Wedin Fig. 1, i. e., in a direction to disengage contact 22 from contact 19; and whenthe contacts 19 and 22 are out of engagement the motor operates to swing arm 20 to the left "to cause engagement of contact 22 with contact .19. "The posttion of arm I l is controlled by the metering element I 5, and hence the above describedmethod of operation-causes a continuous ""hunting operation of't'he motor of such character as to create a definite and'predeterminedreia 3 tion between the rotative position of the motor shaft 26 (Fig. 4) and the position of arm l1.

The motor shaft 26 preferably mounts a disc 21 at its outer end concentric therewith. A carrier plate flat and of substantially ovate form, with a portionthereofprojecting.laterally relative to disc 21. An ear is preferably formed integrally with plate 28 at the above mentioned projecting portion, preferably including a portion 30 bent substan; tially perpendicularly from the plate, and a terminal portion 3| bent outwardly fromportion 30 and lying in a plane parallel/to the plane of-- -min ute movement of the pivoted end of the cam plate 28. An elongated arm 32, bent intermediate its ends to provide a substantially perpendicular off-setting portion 33 and to position the end portions thereof in spaced..,substantially parallel planes, is secured to the terminal portion 3| of the ear of plate 28-by means of screw 34 or the like, which serves as a pivot accommodating relative angular adjustment of-th'e arm 32 on the carrier plate 28. A flat elongated curved.

cam plate '35 is fixedly secured at one end to the off-set outer end of arm 32 and lies in a plane parallel to and has face engagement with a portion of plate 28. As here shown, the cam plate is substantially C-shaped,. and is comparatively 28 is secured to this disc at 29 in face 5 engagement therewith. Plate 28 is preferably portion thereof opposite said 10 said ear j a 4 the metered force, pressure or'condition bears a relationship to the condition to be indicated somewhat difierent from a square root relation, such as a relationship between a 1.7 power and a 2.3 power, or within some other limited range of variation above and below the power for which the cam plate was designed. The cam plate 35 may be adjusted by releasing the clamping plate 31, swinging the cam plate "about member 34 as a pivot to a position corresponding to the proper power or relation, and retightening the clamping plate. The zero point of the cam is not altered appreciably by the adjustment because of the location of the pivot 34, the provision of the reversely curved cam edge 50 and the small or 7, plate, all of which, cooperate to permit the roller 44 to assume the same zero position in adjustments of the cam within its limited range pro- 0, po'rtional to the spacing of point 36 from the opposite end of the cam. The 100% point of the cam is not altered appreciably by the adjustment because of the concentric relation with pivot 34 of the elongated portion of, the edge of thecam.

at the free end portion of the cam. Consequently the adjusted settings of the cam will produce re-' sults as illustrated graphically in Fig. 5 where the curve 45' represents operation of the cam as.

a square root cam, the curveg46 represents opnarrow at the end portion secured to arm 32 and eration with the. cam adjusted for a relation increases in width to terminate in a comparatively wide opposite free 'end portion. The outer edge of cam plate constitutes the cam surface thereof, and a substantial or elongated portion of said edge at the wide free end portion of said 5 plateis substantially concentric with the axis of screw 34. The outer edge of the cam plate at the pivoted end thereof is reversely curved at 50 adjacent to and'facing the pivot axis 34 of said plate with its tip 5| spaced from the axis of 0 shaft 26 a distance lessthan'the spacing of the pivot member 34 from said axis; The concentric edge portion shown extends from approximately the point 36 to the outer end of the cam and is of a length approximately one-fourth of the total length of the cam edge. An elongated clamp plate 31 extends substantially longitudinally and centrally of plate 28 and is secured to plate 28 by screws 38 atone end 'and-39 at an intermediate portion thereof. The outer end of the clamp. plate 31 bears against the face of cam plate 35 opposite that which bears against carrier plate 28, and serves to clamp said plate fiat against said carrier plate.

An indicating pointer 40 is pivoted at 4i .to a

bracket 42 carried by frame l3, and an elongated arm 43 extends from said pivot'and isheldin fixed angular relation to pointer 40. A roller 44 is'journaled on the outer'end of arm 43 and rides upon the upper portion of the outer edge of the cam plate 35, whereby arm 43 serves as the means for operating pointer 40., Assuming that the cam edge of the'cam plate '35 is shaped to function as a square root extracting cam, i. e., in a parabolic curve, swinging 65 of pointer 40 uponrotation 'of the cam will-be according'to a squareroot relation between the applied pressures or force and the condition to be indicated, 'so that the pointer wilLaccurately indicate the condition being measured upon a Js'cale'whose divisions are. substantially equally spaced as shown. The adjustability of the cam V arrangementincreas'es the usefulness of the in strument, however, and enables it'to beused to fractionally less than the square root, and the.

curve 41 represents operation with the cam adjusted for a'relation fractionally greater than the square root. In the graph it is assumed that theinstrument is the same'for' all'cam adjust.-

ments, i. e. that the maximum I measurement; which can be or which is desired to be made by the metering element remains constant. 7

to cube root relations and Variations therefrom,

or to relations varying with respect to any other,

Still another application,

mathematical power. of the invention is to permit cam adjustments to compensate for variations in other relations such as variations from a relation illustrated.

graphically at 48' in Fig. 5, for which special shapes of cam plate 35 must be designed.

I claim: i

of saidear and arm, and releasable meansfor clamping the opposite end of said cam plate against said' carrier. 2. An adjustable cam comprising-a carrier, a

flat cam plate having a cam edge of elongated curved outline including'i a reverselyqcurved end portion, said plate bearing against saidcarrier at one end, means projecting from the sideofsaid plate adjacent the reversely curved end of said plate for pivotally connecting said plate adjacent 1 to its reversely curved end portion to said carrier about an axis spaced from 'the'axis of said carcam edge bears a substantially constant relation to' the axis of said carrier-in all adjustments thereof within a predetermined range, a portion 7 Y e of the-Opposite end of. saidicam edge diametri measure conditu ms;where the relation'between cally opposed to said pivot means being concen the range of the'condition being measured by While the device has beendescribed withrespect to square root relations, it is also applicable 1. An adjustable cam comprising 'a carrier adapted to be mounted on a rotatable member,

rier'whereby said reversely curved end of said trio with said pivot axis, and means for releasably securing the free end portion of said plate to said carrier, said range being proportional to the length of said concentric portion.

3. An adjustable cam as defined in claim 2, wherein said pivot means includes pivotally connected parts off-set relative to said carrier and to the end of said cam plate, respectively.

4. An adjustable cam comprising a carrier, a flat cam plate having an elongated curved cam edge including a reversely curved end portion, means pivoting one end of said plate eccentrically of said carrier and spaced outwardly from said reverse curved end portion whereby the reverse curved end of said cam edge maintains a sub- 'stantially constant spacing from the axis of said carrier in a limited range, the opposite end portion of said cam edge terminating at least 180 displaced from said pivot means and including a portion concentric with said pivot means, and releasable means for locking said plate to said carrier in selected adjustment.

5. An adjustable cam comprising a carrier, a C-shaped fiat plate having a C-shaped cam edge terminating in a reverse curve and adapted for engagement by a cam follower, means for pivoting said plate to said carrier eccentrically of said carrier and spaced from said reversely curved edge whereby the adjacent end of said C-shaped edge maintains a substantially constant relation to the axis of said carrier, and means for releasably clamping said plate to said carrier, an elongated portion of the opposite end of said cam edge being diametrically opposed to and substantially concentric with said pivot means, whereby angular adjustment of said plate upon its pivot varies the relation of said cam edge and cam follower to the axis of said carrier on radii between but not at the diametrically opposed points of engagement of the cam edge and cam follower at which the latter is aligned with the carrier axis and the pivot axis when the concentric edge is diametrically opposed to said plate pivot.

FRANK DONALD BURNS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 359,133 Covel Mar. 8, .1887 868,086 Hanson et al. Oct. 15, 1907 1,083,991 Connet Jan. 13, 1914 1,202,052 Gibson Oct. 24, 1916 1,795,250 Connet Mar. 3, 1931 1,880,933 Elliott Oct. 4, 1932 FOREIGN PATENTS Number Country Date 571,890 Germany Mar. '7, 1933 

